During operation of a vapour compression system, such as a refrigeration system, an air condition system or a heat pump, a compressor forming part of the vapour compression system may create pressure pulsations in the refrigerant circulating in the vapour compression system. Such pressure pulsations may result in wear on other components of the vapour compression system, and may even cause damage to such components. Furthermore, the pressure pulsations may create undesirable noise.
It is therefore desirable to either avoid such pressure pulsations, or to ensure that, if pressure pulsations occur, the pressure pulsations are not causing damage to the other components of the vapour compression system. This may, e.g., be obtained by arranging an absorptive muffler in the refrigerant path.
In the case that the compressor is of a type which operates at a fixed speed, the possible pressure pulsations created by the compressor will normally have a fixed frequency or a frequency within a very narrow frequency band. In this case it is possible to design a pulsation damper which is capable of damping the pressure pulsations of the specific frequency or within the narrow frequency interval, e.g. by means of destructive interference.
US 2010/0218536 A1 discloses a resonator arranged in an economizer line of a refrigeration system. The resonator has a first branch and a second branch. A first flow path length across the resonator through the second branch is longer than a second flow path length across the resonator through the first branch. Thereby pulsations in the refrigerant flowing along the two branches will be out of phase when reaching a manifold and will cancel so that less pulsation is transmitted to the housing. The lengths of the branches are selected to match a specific pulsation frequency, and pulsations having a frequency which differs from the specific pulsation frequency will not be cancelled.
EP 1 831 566 B1 discloses a compressor having a housing and including means for limiting pressure pulsations along a branch path, such as an economizer path. Within a wall of the housing, the branch path includes first, second and third legs. The lengths of the legs are tuned to match a specific pulsation frequency, and pulsations having a frequency which differs from the specific pulsation frequency will not be limited.
When a variable speed compressor is applied in a vapour compression system, pressure pulsations having frequencies within a relatively broad frequency band may occur. It is not possible to cancel such pulsations by means of the devices disclosed in US 2010/0218536 A1 and EP 1 831 566 B1.
U.S. Pat. No. 6,799,657 B2 discloses an absorptive and reactive muffler including an annular flow path for the gas with the centre of the annulus having a plurality of resonators which are in open communication with the downstream end of the annular flow path and make up the reactive portion of the muffler. The flow path is at least partially lined by an absorptive material overlain by a perforate material and makes up the absorptive portion of the muffler.